The present invention relates to a control system for controlling an automatic transmission apparatus installed on a vehicle such as an automobile.
In the past, an automatic transmission control system installed on a vehicle such as an automobile is generally constructed in such a manner as to be able to change the transmission ratio or range of an automatic transmission apparatus in accordance with the running conditions of the vehicle in an automatic fashion. Such a change in the transmission ratio is effected using, as parameters, the running speed of the vehicle and an engine load such as the opening degree of a throttle valve and the like while making reference to a transmission pattern which is previously stored in a control unit.
Further, among these types of automatic transmission control systems, it is also well known that in order to meet various travelling conditions such as driving uphill, driving along a flat surface, etc., a plurality of transmission patterns corresponding respectively to the different travelling conditions are stored in the control unit, and the operator has to select the most appropriate transmission ratios judging from the travelling conditions of the vehicle under which the vehicle is travelling, so that a change in the transmission ratio or range can be made in a suitable manner.
In the above mentioned conventional automatic transmission control system, however, the travelling conditions of the vehicle can not always be detected in a precise manner, and if the operator fails to make an appropriate change or selection among the transmission patterns, there occurs a situation where the selected transmission ratio is too high for ascending a hill, resulting in an insufficient power output characteristic, or an increase in the fuel consumption, or the generation of undesirable noise. Moreover, the operator is forced to perform such a transmission-pattern selecting operation, which is not desirous from the point of view of safety in driving.